A PLC used as a control device for industrial machines or the like includes a base unit and a plurality of units arranged on the base unit. For example, various types of units such as a power supply unit serving as a power source, a CPU unit that manages control of the overall PLC, a motion CPU unit that controls a servomotor with a servo amplifier attached to a driving unit of a production device or an equipment device, an input unit that receives input of a signal from a switch or sensor attached in an appropriate position of a production device or an equipment device, an output unit that outputs a control signal to an actuator or the like, and a communication unit for making connection to a communication network are arbitrarily combined.
The base unit includes a basic base unit and an expansion base unit connected to the basic base unit via an expansion cable. At most one basic base unit can be disposed on a unit configuration. The CPU unit can be attached to only the basic base unit. The expansion base unit can be disposed only when there is a basic base unit. The number of units that can be arranged on a base is restricted by a CPU unit that manages the units. The base unit has slots to which units such as the power supply unit and the CPU unit are attached. Names or numbers such as a power supply slot, a CPU slot, a slot 1, and a slot 2 are assigned to the slots.
A multi CPU system including a PLC having CPU units has a plurality of CPU units attached to a basic base unit, and is used as a system for controlling various units such as an input unit, an output unit and a communication unit, with each CPU unit. In the multi CPU system, positions of slots to which the CPU units can be arranged and the number of the slots are previously defined.
A display used in a control device for industrial machines or the like displays an operation screen created by a user. The display is connected to a PLC or other displays. The user performs control and monitoring of a system through operation on the created screen.
When a control device for a PLC, display or the like is operated, how to construct the system is examined beforehand by the user. Conventionally, when a system is more complicated and larger-sized, a load on the user at the time of system construction is greater. A system construction supporting tool is a tool for reducing the load at the time of system construction.
For example, Patent Literature 1 proposes a technique of a PLC tool device that enables to perform a registration process of CPU units and to display units of which a PLC is constructed for each type in a tree structure. Patent Literature 2 proposes a technique of an engineering supporting system that displays icons of measurement devices and the like on a tree display unit and enables to display connectable connection devices and the like in a list in response to a click of the icon. Patent Literature 3 proposes a technique relating to symbol inputting for a ladder diagram, in which a symbol to be used as an input candidate is searched from an input character string and the search result is displayed on a ladder editor.